A fake modelling agency Instagram account is asking children to send inappropriate images of themselves in an outfit, a bikini and then naked.
The account 'Starlett' has been preying on youngsters by claiming to be a booking agent.
Police have said the children are threatened if they do not send over the pictures, Birmingham Live reports.
Aldersley High School, Wolverhampton, sent out a warning about the social media app to parents after secondary school students were targeted.
A spokesman for the school said: "We have just received this alert from West Midlands Police. If your child uses Instagram please share this with them.
"We have had information that students at a number of secondary schools across Staffordshire, Stoke and Cheshire East have been contacted by a bogus modelling company, 'Starlett or Scarlett Bookings Agency' on Instagram pressurising young people into sending inappropriate images.
"Initially, these requests will be modelling their favourite outfits, then a bikini shoot and finally a naked photo to analyse their body type coupled with threats if not forthcoming."
The warning has been issued across a wide area. Cheshire Police say they are investigating the agency.
A spokeswoman said: "We have been made aware of concerns about a modelling agency contacting young people on social media platforms.
"I’d like to reassure you we are looking into this."
The CEOP (Child Exploitation and Online Protection) website allows parents to report concerns online and to discover how young people can stay safe online from issues such as online abuse or sexual exploitation.
Parents can also find further online safety advice from Thinkuknow or the NSPCC if they are worried about online safety, people acting inappropriately online, or if they fear their child is being sexually abused or groomed.
